CN113939199B

CN113939199B - System for roasting coffee beans

Info

Publication number: CN113939199B
Application number: CN202080042507.7A
Authority: CN
Inventors: J·莫兰德; S·切卡罗利; F·F·迪比耶夫; T·迪格雷弗; B·范戴克; R·D·M·莱蒙斯; M·A·塞利斯; C·范巴万什沃
Original assignee: Societe des Produits Nestle SA
Current assignee: Societe des Produits Nestle SA
Priority date: 2019-06-20
Filing date: 2020-06-19
Publication date: 2023-12-01
Anticipated expiration: 2040-06-19
Also published as: JP2022537262A; CA3143445A1; BR112021024261A2; ZA202200461B; US20220304361A1; CN113939199A; EP3986167A1; KR20220020808A; MX2021014563A; WO2020254635A1; IL287944A; AU2020298097A1; SG11202112763UA

Abstract

The present invention relates to a system for roasting coffee beans, the system comprising: -a torrefaction device (1) generating flue gas, and-a flue gas treatment unit (2) configured to collect and treat the flue gas generated by the torrefaction device, wherein: -the baking apparatus comprises a flue gas outlet (11), and-the flue gas treatment unit comprises: a flue gas inlet (21) configured to cooperate with a flue gas outlet of a baking apparatus, a flue gas filtration subunit (22) comprising at least an activated carbon filter (221), a flue gas driver (23) configured to circulate flue gas from the flue gas collection device to an outlet (25) of the flue gas treatment unit through the flue gas treatment unit, wherein the flue gas treatment unit (2) comprises an air inlet (24) configured to mix flue gas generated by the baking apparatus (1) with ambient air before circulating the flue gas through the flue gas filtration subunit (22).

Description

System for roasting coffee beans

Technical Field

The present invention relates to an apparatus for roasting coffee beans in a safe environment.

Background

Roasting coffee beans is a well known process. The main steps include heating the coffee beans to a desired roasting level and then cooling or quenching the heated coffee beans to stop roasting. During heating, fumes are emitted. This flue gas contains all safe and desirable components, in particular the usual roast coffee aroma, but also undesirable less safe Volatile Organic Compounds (VOC) such as pyridine, 2-furanmethanol, caffeine furfural, formaldehyde, acetaldehyde.

However, a recent trend is to carry out small batches of roasting with small roasting machines in shops, restaurants and cafes where customers can consume coffee brewed from freshly roasted coffee beans. The roasting machine not only provides the advantages of freshness and theatres, but also distributes a pleasant roasted coffee aroma within a store or cafe.

However, as described above, harmful components may also be emitted. When the roasting machine is used in a closed environment, such as a shop, cafe or restaurant, the emission of some components may become harmful depending on the size of the room, ventilation of the room.

In such an environment, it is therefore recommended to stop the discharge of fumes from the baking machine, in order to avoid any health problems for the people present in the store. Existing solutions include filtration, use of catalytic converters and/or electrostatic precipitators to capture or destroy flue gas components.

Depending on the type of solution used for treating the flue gas, the high temperature of the flue gas may have a detrimental effect on the flue gas treatment device. In particular, filters made of activated carbon are typically positioned in filtration modules. If flue gas having a temperature above a certain temperature passes through such a filter, it may be damaged or not operate properly.

Conversely, if the filtration solution is a catalytic converter operating at a temperature above 300 ℃, high temperature flue gas may be required.

In existing solutions, fans are often used to drive flue gas to filter solutions, and this fan can generate a lot of noise, which is undesirable in public areas such as shops or restaurants.

The object of the present invention is to solve the problem of controlling the temperature of the flue gas dispensed by a coffee bean roasting machine after the flue gas has been treated by a filtering solution.

The object of the present invention is to solve the problem of protecting filters such as activated carbon from the heat of the flue gas dispensed by coffee bean roasting machines.

Another object is to provide a solution that does not generate excessive noise.

Disclosure of Invention

In a first aspect of the invention, there is provided a system for roasting coffee beans, the system comprising:

-a baking apparatus, said apparatus generating flue gas, and

-a fume treatment unit configured to collect and treat fumes generated by the baking apparatus, wherein:

the baking apparatus comprises a flue gas outlet, and

-the flue gas treatment unit comprises:

a flue gas inlet configured to collect flue gas,

a smoke filtering subunit, wherein the smoke filtering subunit,

a flue gas driver configured to circulate flue gas from the flue gas collection device to an outlet of the flue gas treatment unit through the flue gas treatment unit,

Wherein the system comprises an air inlet device configured to mix flue gas generated by the torrefaction device with ambient air in order to control the temperature of the flue gas within the flue gas filtration subunit.

The system involves roasting coffee beans by means of two devices: first, a roasting apparatus in which coffee beans are heated to be roasted; and second, a fume treatment unit configured to treat fume generated in the first roasting device during roasting of the coffee beans.

The two devices may be sub-components of a single main system or, alternatively, may be considered as separate modules that cooperate during the baking process.

Any type of baking apparatus may be used. In the roasting apparatus, the coffee beans are heated and preferably mixed to homogenize the heating of the coffee beans.

The heating source may be a burner (meaning combustion) fed by natural gas, liquefied Petroleum Gas (LPG) or even wood. Alternatively, the heat source may be a resistor, a ceramic heater, a halogen source, an infrared source, or a microwave source.

Preferably, the heating source is electric, such that the air pollutants generated during roasting are pollutants generated solely by the heating of the coffee beans themselves, and not by the combustion of gases that occur when the heating source is a gas burner using natural gas, propane, liquefied Petroleum Gas (LPG) or even wood.

During the roasting operation, the mixing of the coffee beans may be obtained mechanically with a fluidized bed of hot air or with stirring blades or a drum.

Preferably, the baking apparatus is a hot air fluidized bed chamber. In such chambers, heated air is forced through a screen or perforated plate under the beans with sufficient force to lift the beans. As the beans tumble and circulate within this fluidized bed, heat is transferred to the beans.

Alternatively, the roasting apparatus may be a cartridge chamber in which the coffee beans are tumbled in a heated environment. The cartridge chamber may consist of a cartridge that rotates along a horizontal axis, or the cartridge chamber may include stirring vanes to tumble the coffee beans in a heated environment.

The torrefaction device comprises an outlet from which flue gases generated during the torrefaction operation can be discharged.

The flue gas treatment unit of the system comprises a flue gas inlet configured to cooperate with and collect flue gas through this flue gas outlet of the torrefaction device.

The flue gas treatment unit of the system comprises a flue gas filtration subunit. This subunit treats the flue gas in order to reduce or eliminate the harmful pollutants contained in the flue gas.

This subunit may include:

an active treatment unit to destroy contaminants within the plant, such as an afterburner or catalytic afterburner capable of thermally oxidizing the contaminants,

Or (b)

A passive treatment unit, such as a mechanical filter (wire mesh or filter paper), an activated carbon filter or an electrostatic precipitator, which leaves the contaminants inside the plant,

or (b)

A unit for transferring contaminants out of the room (such as a pipe connected to the outside of the room), or a combination of the above units.

Afterburners will be exposed to very high temperatures (typically above 700 ℃) of contaminants such as CO and CO ₂ Thermally oxidizes and converts them to ash.

The catalytic converter comprises a ceramic substrate coated with a catalytic impregnant comprising nanoparticles of noble metals such as copper oxide, nanoparticles of iron oxide, and one or more metals of the platinum group in general (platinum, palladium, rhodium). The operation of the catalytic afterburner requires lower temperatures than the afterburner: the temperature is typically comprised between 300 ℃ and 500 ℃. Conveniently, although not necessarily, the flue gas is preheated prior to its entry into the catalytic converter, typically by means of a heat exchanger fed by the flue gas exiting the catalytic converter.

Filters are generally capable of retaining Volatile Organic Compounds (VOCs), hydrocarbons, and Particulate Matter (PM). The flue gas treatment unit may comprise several filters, depending on their ability to retain specific pollutants. The filter configured for capturing VOCs and hydrocarbons is preferably an activated carbon filter or a charcoal filter. The filter configured for trapping particulate matter is preferably a High Efficiency Particulate Accumulator (HEPA) filter, a metal filter (e.g., an ultrafine steel wool media filter). Electrostatic precipitators may be used to trap PM and VOCs.

In a preferred embodiment, the smoke filter subunit may comprise at least an activated carbon filter. Such filters adsorb Volatile Organic Compounds (VOCs). This filter requires specific operating conditions in terms of temperature.

Typically, such carbon filters require temperatures below 65 ℃. Above such temperatures, activated carbon filters may produce VOCs rather than retain these compounds.

Preferably, the carbon filter operates at a temperature of at least 50 ℃. Below such temperatures, efficient filtration requires longer residence time of the flue gas in the activated carbon filter, and low temperature management and long residence time may be difficult to achieve.

In this preferred embodiment, the fume filtration subunit typically comprises at least one additional filter that operates without heating. The at least one additional filter is intended to retain at least other types of contaminants besides VOCs, such as:

large Particulate Matter (PM) with a particle size of more than 2.5 μm. Such particulates may be captured by a HEPA filter (high efficiency particulate accumulator). Such large particulates can be white plume fumes and small particulates:

fine bran which can be captured by ultrafine steel wool media filters or metal meshes,

Small particulate matter (PM 2.5). These particles may be captured by an electrostatic precipitator.

Preferably, the smoke filter subunit comprises in turn at least one filter to remove particulate matter, and then an activated carbon filter, depending on the direction of the smoke flow within the smoke treatment unit. This sequence prevents clogging of the carbon filter with particulate matter.

Preferably, if an electrostatic precipitator is implemented, it is physically positioned below the activated carbon filter. Thus, when the electrostatic precipitator is turned off, for example during cleaning and/or maintenance of the flue gas treatment unit, particles falling from the electrostatic precipitator due to gravity do not fall onto the activated carbon filter.

According to a preferred embodiment, the fume filtration subunit comprises, in sequence, in accordance with the movement of the fume flow within the fume treatment unit: HEPA filters, electrostatic precipitators, then activated carbon filters.

Preferably, in this embodiment, the carbon filter is physically positioned above the electrostatic precipitator. Thus, the flue gas is introduced upwards through the subsequent device.

The flue gas is driven into the flue gas treatment unit and a different filter by means of a flue gas driver configured to circulate flue gas from the flue gas collection device to an outlet of the flue gas treatment unit through the flue gas treatment unit. At the outlet, the flue gas can be safely released into the atmosphere of the room, as the contaminants have been trapped.

The flue gas driver is typically a fan that drives the flue gas to the outlet.

Preferably, the fan is positioned close to the outlet of the flue gas treatment unit. Thus, the fan is not contaminated by untreated flue gas and its maintenance is easier.

The flue gas treatment unit may comprise a VOC sensor and/or a PM sensor, preferably positioned after the carbon filter. An alarm may be provided if the level of VOC or PM exceeds some predetermined level.

The system includes an air inlet device configured to mix flue gas generated by the torrefaction device with ambient air in order to control a temperature of the flue gas within the flue gas filtration subunit.

Ambient air may be drawn directly from the room in which the system is installed.

This air inlet device is typically positioned at a location upstream of the smoke filter subunit and, if the smoke filter subunit comprises an activated carbon filter, upstream of said activated carbon filter.

Thus, the flue gas is mixed with ambient air (i.e. air having a temperature below 40 ℃, typically below 25 ℃) before the flue gas is treated by the activated carbon filter, which has the effect that the temperature of the flue gas collected from the flue gas outlet is reduced. The temperature at the flue gas outlet of the baking apparatus often reaches above 65 ℃, but again mixes with ambient air and the flue gas temperature is reduced in order to avoid malfunctions of the activated carbon filter in the flue gas filtration subunit.

The air inlet of the flue gas treatment unit may be designed to introduce a certain amount of ambient air into the flue gas in order to substantially reduce the flue gas temperature at the activated carbon filter. This design may in part determine the ratio of air volume to flue gas volume required to reach the desired temperature. This ratio can also be controlled by adjusting the power of the flue gas driver, as described in more detail below.

Preferably, the flue gas treatment unit comprises at least one temperature sensor configured for monitoring the temperature within the unit. When the flue gas treatment unit comprises an activated carbon filter, at least one temperature sensor is positioned in front of the activated carbon filter. The temperature sensor realizes the temperature control of the flue gas near the activated carbon filter which needs a specific working temperature range. If the temperature is outside the operating range, a temperature sensor may be used to provide an alarm.

In one embodiment, the air inlet means is positioned and designed to introduce both air and flue gas at the same point within the flue gas treatment unit. By introducing air and flue gas simultaneously at a single point within the flue gas treatment unit, the flows of both gases have similar orientations within the flue gas treatment unit, and thus the force required to drive them within this unit becomes less important than if they were introduced at different points and in different directions within the flue gas treatment unit.

In particular, when the flue gas driver is a fan, which is typically located close to the outlet of the flue gas treatment unit, the fan speed may be kept within a range that does not generate too much noise around the flue gas treatment unit.

Preferably, the air inlet is designed to surround the flue gas inlet. This design has the advantage that smoke is prevented from escaping into the room at the connection between the baking apparatus and the smoke treatment unit.

Preferably, the air inlet device comprises:

-a first wall extending between a flue gas outlet of the torrefaction device and a flue gas inlet of the flue gas treatment unit, and

-at least one hole through said wall.

The first wall enables connection of the flue gas outlet of the torrefaction device with the flue gas inlet of the flue gas treatment unit and guides the flue gas between the two devices. At least one aperture provides access to the ambient atmosphere and effects the introduction of air within the channel formed by the first wall. Typically, the holes are small openings pierced in the flat wall.

Thus, the flue gas is led to the flue gas treatment unit and at the same time air is led in and mixed.

Generally, the number and size of the holes are set to provide a minimum ratio of air volume to flue gas volume to achieve a minimum speed of the flue gas driver components of the system. Typically, the minimum ratio of air volume/flue gas volume is about 1.

This minimum ratio generally ensures that the connection between the flue gas outlet of the baking apparatus and the flue gas inlet of the flue gas treatment unit is not too tight, which may affect the pressure within the baking apparatus during the baking operation and directly the baking operation, especially if the baking apparatus comprises an air drive to form a fluidized bed.

This minimum ratio of air volume to flue gas volume can be increased by: adjusting the flow rate of the flue gas extracted by the flue gas driver of the flue gas treatment unit (particularly the fan speed of the flue gas driver); this flow rate is accurately increased from a minimum predetermined flow rate.

This ratio may be defined by considering the following: the type of baking equipment (e.g. the baking machine may produce a large volume of flue gas, the design of the flue gas outlet), the type of flue gas treatment unit (meaning a high air flow if this unit has to be operated at a lower temperature, or conversely a small amount of air if it is operated at a high temperature).

In a specific embodiment, the first wall of the air inlet device may comprise: at least two bars for connecting a flue gas outlet of the baking apparatus to a flue gas inlet of the flue gas treatment unit; and a space extending between two adjacent rods and defining an aperture.

In one embodiment of the air inlet device, at least one aperture may be covered by a mesh. The mesh is protective and prevents the introduction of small debris such as large size dust, insects, or fingers, but does not limit the introduction of ambient air.

In one embodiment, only one region of the profile of the first wall of the air inlet device comprises at least one aperture.

The location of the holes in one specific area of the contour of the first wall enables the introduction of ambient air from a specific area around the system in order to stabilize the air flow into the device. This configuration is particularly useful where the system is used in shops and cafes where ambient air around the system flows in an irregular manner due to frequent door opening, customer movement, or in semi-open shops and cafes. Providing a wall with a zone comprising all holes and orienting the zone in a room where the movement of ambient air is more stable avoids introducing an irregular flow of ambient air within the flue gas treatment unit, which introduction may affect the treatment of flue gas in the filtration subunit.

Preferably, the air inlet means comprises an outer wall surrounding at least a portion of the first wall including the at least one aperture, and the first wall and the outer wall are separated by a gap.

The outer wall surrounds at least that portion of the first wall that includes one or more apertures. The location of this outer wall thus provides protection in front of the holes and stabilizes the air before it enters through the holes.

In a preferred embodiment, the outer wall is a ring completely surrounding the first wall.

In this preferred embodiment, if several holes are provided in the first wall, they may be regularly positioned along the circumference of said first wall.

Alternatively, the outer wall may take on the shape of a scallop, each tooth face of the scallop facing one of the holes in the first wall.

In one embodiment, the air inlet device includes at least one size adjustment member to adjust the size of at least one aperture included in the first wall.

Thus, depending on the size of the aperture, the flow rate of ambient air introduced into the flue gas inlet and its ratio to flue gas can be adjusted without the need to use another air inlet device in the system or to adjust the flow rate extracted by the flue gas driver of the flue gas treatment unit.

Alternatively, to provide a more flexible way to control the amount of air introduced into the flue gas treatment unit, both the size adjustment component and the flow rate driven by the flue gas driver (i.e. typically the fan speed of the flue gas driver) may be modified.

If the air inlet device comprises several holes in its first wall, the size adjustment means may be configured to adjust the size of all holes of the air inlet device at the same time, or one size adjustment means may be provided for each hole of the air inlet device.

Generally, the size adjustment member effects adjustment of the size of the at least one aperture from fully open to fully closed.

The fully closed position corresponds to a particular use of the system that generally does not correspond to a baking operation of the baking apparatus. Indeed, as mentioned above, the lack of open holes to introduce air may affect the pressure within the roasting apparatus during the roasting operation and directly the roasting operation, especially if the roasting apparatus comprises an air drive to form a fluidized bed. However, the fully closed position may be of interest during cleaning operations of the system, in particular in drying operations of the filtration subunits of the flue gas treatment unit as detailed below.

In one manual mode, the size adjustment feature may be manually controlled by a system operator. For example, when a particular fume treatment unit is associated with a particular baking apparatus, this manual control may be set in a configuration step of the system. Based on the specifications of the two devices, the operator can fix the size of at least one aperture to achieve a particular ratio of air to flue gas.

For example, during a baking operation, an operator may wish to improve the performance of a flue gas treatment unit comprising an activated carbon filter by avoiding excessive temperatures and by introducing a large amount of air in the mixture of flue gas and air. This setting takes into account the temperature and flow rate of the flue gas produced by the particular torrefaction device used in the system.

In another cleaning operation of the flue gas treatment unit, an operator may wish to introduce a high temperature gas stream within the flue gas filtration unit, for example to dry some of the wet components of the filtration subunit. In this mode, it is desirable to have a maximum temperature and at least one aperture may be fully closed to take advantage of the benefits of the high temperature gas produced by the baking apparatus without mixing it with cooler ambient air.

In one automatic mode, the system may include at least one actuation device to control the size adjustment member, and the system includes a control system operable to control the actuation device.

In this mode, the size adjustment member is moved by an actuating means such as a motor controlled by the control system of the system.

If several holes are present, one size adjustment member and one actuation means may be constructed to adjust the size of the holes simultaneously. In more complex systems, different size adjustment members may be provided, each of them or some of them being moved by different actuation means. This implementation enables customizing the air inlet device for different types of systems (different baking equipment and different flue gas treatment units), in different types of rooms (as described above, depending on the room, closing the holes in one zone of the first wall of the air inlet device) and for different modes (baking, cleaning).

The control system controlling this actuation means may be the control system of the torrefaction device or the control system of the smoke filter unit.

In a preferred embodiment of the automatic mode, the flue gas treatment unit may comprise at least one temperature sensor configured for monitoring the temperature within said unit, and the control system is arranged to control the at least one actuation means of the at least one size adjustment member based at least on the monitored temperature within the flue gas treatment unit.

Based on the temperature set point, the temperature within the flue gas treatment unit may be controlled by: the at least one aperture is sized to decrease the temperature within the flue gas treatment unit and the at least one aperture is sized to increase the temperature within the flue gas treatment unit.

This implementation may be particularly useful if the flow of flue gas produced by the torrefaction device is not constant.

In particular, during the operation of roasting the coffee beans, the size of the at least one aperture may be increased from the beginning to the end of the roasting operation, so that less air is introduced at the beginning of the roasting operation and more air is introduced at the end of the roasting operation. In fact, at the beginning of the roasting operation, the fumes produced by roasting the beans are less hot than at the end of the roasting operation. Furthermore, if the torrefaction operation occurs in a system that has not been in use for a period of time, the internal components of this system, such as the components upstream of the filtration subunit, are cold and absorb the heat of the flue gas before it reaches the filtration subunit. Thus, it is less desirable to introduce too much ambient air into the flue gas. In contrast, at the end of the baking operation, the flue gas is particularly hot, and it becomes necessary to introduce more ambient air into the flue gas treatment unit.

Preferably, the above-mentioned control system is arranged to control the actuation means and the flue gas driver of the flue gas treatment unit based at least on the monitored temperature within the flue gas treatment unit.

The power of the flue gas driver may be adjusted to drive more or less air into the flue gas treatment unit and to reduce or raise the temperature within the flue gas treatment unit, respectively. This control essentially comprises adjusting the flow rate of the flue gas in the flue gas treatment unit, in particular by adjusting the fan speed.

In a specific embodiment, the control system may be arranged to control the flue gas driver of the flue gas treatment unit based at least on the size of the at least one aperture of the air inlet device.

In fact, when the size of at least one aperture becomes particularly small, maintaining a certain level of suction in the flue gas treatment unit may change the pressure in the baking apparatus as described above. Thus, during the baking operation, in case the at least one aperture has a predetermined opening size, the power of the flue gas driver may be automatically reduced, respectively, to avoid an excessively strong suction force of the flue gas and a variation of the pressure in the baking chamber.

The flue gas driver may also be controlled based on other factors than the size of the holes, such as noise generated by the fan.

When the system does not comprise a size adjustment member and the at least one aperture is fixed, preferably the flue gas treatment unit comprises at least one temperature sensor configured to monitor the temperature within the unit, and the control system is arranged to control the flue gas driver of the flue gas treatment unit based on temperature measurements provided by the temperature sensor.

Typically, the controller is adapted to control the temperature of the flue gas at the location of the carbon filter.

The air inlet device may be part of the torrefaction apparatus or part of the flue gas treatment unit or may be a separate device connectable to the torrefaction apparatus and the flue gas treatment unit.

By a part is meant that the air inlet means is considered to be part of the apparatus.

The air inlet means may be fully integrated within the roasting apparatus. In this case, the air inlet means may be designed to achieve an introduction of an air flow with a minimum predetermined ratio of air flow to flue gas generated by the specific torrefaction device.

Similarly, the air inlet device may be fully integrated within the flue gas treatment unit. In this case, the air inlet means may be designed to achieve an introduction of an air flow with a predetermined minimum ratio to the flue gas for an efficient treatment by said flue gas treatment unit, in particular taking into account the performance of the flue gas driver and the optimal operating temperature of the filtering subunit.

In the last case, the air inlet device may be a separate device that can be used to upgrade the system of the torrefaction apparatus and the flue gas treatment unit.

In a second aspect, there is provided an apparatus for connecting a flue gas outlet of a coffee bean roasting apparatus and a flue gas inlet of a flue gas treatment unit configured to collect and treat flue gas generated by the roasting apparatus, the apparatus being configured to introduce ambient air and mix it with flue gas generated by the roasting apparatus within the flue gas treatment unit, wherein the apparatus comprises:

-at least one hole through said wall.

Preferably, the apparatus comprises an interface configured to mate with a flue gas outlet of the torrefaction device and an interface to mate with a flue gas inlet of the flue gas treatment unit.

In a third aspect, a coffee bean roasting apparatus comprising a flue gas outlet is provided, wherein the apparatus comprises an air inlet device connected to the flue gas outlet, the device comprising:

a first wall extending and protruding from the flue gas outlet of the baking apparatus, and

-at least one hole through said wall.

In one embodiment, the air inlet device may comprise an interface for mating with a flue gas inlet of the flue gas treatment unit.

In a fourth aspect, there is provided a flue gas treatment unit configured to collect and treat flue gas generated by a torrefaction device, the flue gas treatment unit comprising:

-a flue gas inlet configured to collect flue gas, and

smoke filtering subunit, and

wherein the flue gas treatment unit comprises an air inlet device configured to mix the flue gas with ambient air before circulating the flue gas through the flue gas filtration subunit.

In one embodiment, an air inlet device may be connected to the flue gas inlet, and the device may comprise:

a first wall extending from and protruding from the flue gas inlet, and

-at least one hole through said wall.

In one embodiment, the air inlet means may comprise an interface for mating with a flue gas outlet of the torrefaction device.

The fume treatment unit has the same features mentioned in the first aspect, except that it is a module that is independent of the baking apparatus and that is connectable to different types of baking apparatuses.

In a fifth aspect, there is provided a method for roasting coffee beans with a system such as described above and filtering flue gas generated during roasting of said beans, wherein a flue gas driver of the flue gas treatment unit is controlled to adjust the amount of ambient air within the flue gas treatment unit in order to control the flue gas temperature within the flue gas filtration subunit.

Controlling typically includes adjusting the power of the airflow driver or the fan speed of the airflow driver.

When the flue gas treatment unit comprises an activated carbon filter, the flue gas drive of the flue gas treatment unit is controlled to introduce a quantity of ambient air into the flue gas in order to obtain a temperature of the flue gas of at most 65 ℃, preferably at least 50 ℃ at the activated carbon filter.

In order to reach temperatures below 50 ℃, a larger ratio of air volume to flue gas volume is required, which means a higher power of the flue gas driver and a higher flow rate of the mixture of flue gas and air, resulting in a short contact time of this mixture with the activated carbon filter. This short time may not be sufficient to eliminate all contaminants in the flue gas. Furthermore, the high power and high flow rate cause more noise of the flue gas driver, which is always undesirable when the system is installed in a room. For this reason, if there is no other way to increase the amount of air (especially if the design of the air inlet is fixed), it is preferable to keep the flue gas temperature at the activated carbon filter above 50 ℃.

In one embodiment, the control of the air flow driver and, correspondingly, the temperature in the flue gas treatment unit during roasting of the coffee beans in the roasting device may be based on monitoring of the temperature in the flue gas treatment unit.

In another embodiment, the control of the air flow driver and, correspondingly, the temperature in the flue gas treatment unit during roasting of the coffee beans in the roasting apparatus may be predetermined based on a predetermined roasting curve implemented in the roasting apparatus.

In a sixth aspect, a method for roasting coffee beans and filtering flue gas generated during roasting of the coffee beans with a system comprising an air inlet device having at least one size adjustment member to adjust the size of at least one hole comprised in a first wall, such as described above, is provided, the method comprising the step of adjusting the size of at least one hole comprised in the first wall of the air inlet device in order to control the temperature within the flue gas filtering subunit.

Preferably, the size of the at least one aperture is increased in order to reduce the temperature within the flue gas treatment unit, or the size of the at least one aperture is decreased in order to increase the temperature within the flue gas filtration subunit.

Additionally, the method may include the step of controlling the air drive to adjust the temperature within the flue gas treatment unit.

In one embodiment, the adjustment of the dimensions and the corresponding control of the temperature in the flue gas treatment unit during roasting of the coffee beans in the roasting apparatus may be based on monitoring of the temperature in the flue gas treatment unit.

In another embodiment, the adjustment of the dimensions and accordingly the control of the temperature in the flue gas treatment unit during roasting of the coffee beans in the roasting apparatus may be predetermined based on a predetermined roasting curve implemented in the roasting apparatus.

In the present application, the term "filter" relates to any device capable of removing pollutants in flue gas by any physical process such as screening, trapping, adsorption, absorption, electrostatic trapping.

The above aspects of the application may be combined in any suitable combination. Furthermore, various features herein may be combined with one or more of the above aspects to provide combinations other than those specifically shown and described. Further objects and advantageous features of the application will be apparent from the claims, the detailed description and the accompanying drawings.

Drawings

Specific embodiments of the present invention will now be further described, by way of example, with reference to the following drawings.

Fig. 1 is a view of a system according to the invention, showing the path of flue gases through the system,

figure 2 is a detailed view of the collection device and air inlet of the system of figure 1,

fig. 3 is a view of another system according to the invention, showing the path of the flue gases through the system,

figure 4 is a detailed view of the collection means and air inlet of the system of figure 3,

figures 5 to 10 show different embodiments of an air inlet device according to the invention,

figure 11 shows an alternative position of the fume treatment unit with respect to the baking apparatus,

fig. 12 is a block diagram of a controller of a system according to the invention.

Detailed Description

System for baking

Fig. 1 and 2 show an exemplary view of a system of a torrefaction device 1 and a flue gas treatment unit 2. Functionally, the roasting apparatus is operable to roast coffee beans and the fume treatment unit is operable to treat fume generated by the roasting apparatus during roasting.

Baking equipment

The roasting apparatus 1 is operable to contain and roast coffee beans within a roasting chamber 12.

Preferably, the roasting apparatus 1 comprises a roasting chamber 12 into which a flow of hot air is introduced to agitate and heat the coffee beans. The hot air flow is typically generated by an air flow driver and a heater. These devices are positioned below the roasting chamber and introduce a flow of hot air through the bottom of the roasting chamber. In the shown figures, the bottom of the chamber is configured to enable air to pass through, in particular it may be a perforated plate on which the coffee beans may be located and through which the air may flow upwards.

The airflow driver is operable to generate an airflow upwardly in the direction of the container bottom. The resulting stream is configured to heat the coffee beans and agitate and lift the coffee beans. Thus, the coffee beans are heated uniformly. In particular, the airflow driver may be a fan powered by a motor. An air inlet may be provided in the base of the housing to feed air into the housing, the air flow driver blowing this air in the direction of the chamber 12.

The heater is operable to heat the air flow generated by the air flow driver. Preferably, the heater is an electrical resistor positioned between the fan and the perforated plate, as a result of which the air flow is heated to heat and lift the coffee beans before entering the chamber 12.

The heater and/or fan is operable to apply a roasting curve to the coffee beans, the roasting curve being defined as a curve of temperature versus time.

The roasted coffee beans generate a flue gas, which is driven to the top opening 121 of the roasting chamber due to the air flow generated by the air flow driver, as indicated by arrow S1 in fig. 1.

Generally, the bran collector is in fluid communication with the top opening 121 of the chamber to receive bran that gradually separates from the coffee beans during roasting and is blown to the bran collector due to its lighter density.

The remainder of the flue gas is discharged through a flue gas outlet 11 located at the top of the baking apparatus.

Flue gas treatment unit

The flue gas treatment unit 2 is operable to receive and treat flue gas S1 emanating at a flue gas outlet 11 of the baking apparatus.

First, the flue gas treatment unit 2 comprises a flue gas inlet 21 adapted to collect flue gas. This flue gas inlet 21 is shown in particular in the exploded view of fig. 2: the collecting means forms an internal void space, guiding the flue gas from the outlet 11 of the baking apparatus in the direction of the flue gas filtering subunit 22 (dashed lines S1, S2, S3). In fig. 2, it can be appreciated that the bottom part of the flue gas collection device comprises holes 211 designed to fit in a loose manner with the flue gas outlet 11 of the baking apparatus, the holes 211 being much larger than the cross section of the flue gas outlet end of the baking apparatus. Generally, the bottom part of the fume collection device is simply placed above the top of the baking unit without any fixing means. This is particularly practical when the torrefaction unit 1 and the flue gas treatment unit 2 are two separate modules. The fume treatment unit 2 may be easily connected or disconnected from any baking equipment. This loose fit is not airtight and does not create a vacuum in the baking apparatus that would affect the baking operation, especially if the baking occurs in a fluidized bed.

The collecting means comprises a flue gas outlet 212 cooperating with a guiding duct 27, which guides the flue gas to a second part of the flue gas treatment unit, namely the flue gas filtration subunit 22. In the embodiment shown, the guide duct 27 is designed to let the flue gases downwards in order to pass through the different filter devices from bottom to top. However, in other not shown embodiments, the guiding duct may be designed to guide the flue gas through different filter devices from top to bottom.

In the illustrated embodiment, the fume filtration subunit 22 is positioned adjacent and beside the baking apparatus. In other embodiments as shown in fig. 11, the fume filtration subunit 22 may be positioned at a remote location, such as below a counter top upon which the baking apparatus 1 is placed. In such embodiments, the shape of the guide duct 27 is adapted to establish a connection between the different components of the flue gas treatment unit.

The flue gas filtration subunit 22 comprises an activated carbon filter 221 adapted to remove VOCs in the flue gas. Furthermore, in the particularly illustrated embodiment, the flue gas filtration subunit 22 comprises a filter for particulate matter, such as a device 223 adapted to filter large particulate matter PM10 (e.g. a HEPA filter) and a device 222 adapted to filter small particulate matter PM2.5 (e.g. an electrostatic precipitator). Preferably, the means for removing particulate matter is positioned upstream of the carbon filter. This upstream location ensures that the particulate matter does not contaminate the carbon filter.

Physically, the electrostatic precipitator is positioned below the activated carbon filter to avoid particles falling from the electrostatic precipitator onto the activated carbon filter when the electrostatic precipitator is turned off.

Third, the fume filtration subunit 22 comprises a fume drive 23, typically a fan, for drawing contaminated fume through the fume filtration subunit 22, where the fume is treated, from the inlet 211 of the collecting device to the outlet 25 of the fume filtration subunit 22, where the fume is safely distributed into the ambient atmosphere.

Finally, the fume treatment unit comprises an air inlet 24 along the passage defined for the fume and upstream of the fume filtration subunit 22. In the embodiment shown, this air inlet 24 is positioned in the flue gas inlet 21. This air inlet is a simple opening to the ambient atmosphere, eventually protected by a grid to avoid particle ingress. Due to the suction function of the flue gas driver 23, the ambient air flow a is sucked and mixed with the flue gas S1 within the flue gas treatment unit 22. Since the temperature of the ambient air is typically up to 40 ℃, i.e. well below the temperature of the flue gas at the outlet of the baking apparatus, the temperature of the resulting gas mixture S2 is reduced. The air inlet is configured to enable the resulting temperature of the mixture S2, preferably comprised between 50 ℃ and 65 ℃, to be optimally treated for the flue gas by means of the activated carbon filter 221.

The design of the air inlet may in part determine the ratio of air volume to flue gas volume required to reach the desired temperature. Based on the fixed design of the air inlet, the ratio of air volume to flue gas volume can also be controlled by adjusting the power of the flue gas driver (i.e. the flow of air mixed with the flue gas). Since the flow of flue gas S1 is controlled only by the torrefaction device, increasing or decreasing the power of the flue gas driver only affects the volume of ambient air a introduced through the air inlet.

The ratio adjustments made by the flue gas driver power are managed to control the temperature at the activated carbon filter. In addition, other secondary conditions may be considered, such as:

-noise generated by the flue gas driver at high flow rates. It must be noted that implementing the flue gas driver at high power may create a noisy environment, which is always undesirable in a shop environment.

At high flow rates, the contact time of the fumes with the filter is reduced. Since the high power of the flue gas driver means a high flow rate of flue gas through the flue gas treatment unit, this may lead to insufficient contact time in the different filters, in particular within the activated carbon filter 221, which has the effect of distributing contaminants into the atmosphere at the outlet 25 of the flue gas treatment unit.

Finally, the design of the air inlet 24 is preferably defined as:

limiting the pressure drop at the flue gas outlet 11 of the torrefaction device, as the pressure drop may affect the upstream processes of the torrefaction; this can be achieved by providing a sufficiently large air inlet,

and

preventing the flow of flue gases through this air inlet 24 into the ambient atmosphere, which may occur if this air inlet is too large.

The air inlet 24 may be positioned downstream of the flue gas inlet 21 as long as it remains upstream of the carbon filter 221.

The effect of such flue gas temperature control is to effectively treat the flue gas through the activated carbon filter, thereby ensuring effective adsorption of VOCs and avoiding the discharge of VOCs by the activated carbon filter itself at high temperatures, typically above 65 ℃.

Fig. 3 shows a variant of the system of fig. 1 and 2: the system comprises the same torrefaction device 1 and a similar flue gas treatment unit 2, with the difference that the flue gas inlet 21 and the air inlet 24 are slightly different.

In fig. 4, it can be appreciated that at the interface between the flue gas inlet 21 and the flue gas outlet 11, an air inlet device 24 is provided. Due to the suction function of the flue gas driver 23, the ambient air flow a is sucked and mixed with the flue gas S1 within the flue gas treatment unit 22. This means 24 introduces ambient air (shown by arrow a) into the flue gas S1 generated by the baking device and mixes this air with this flue gas in the flue gas treatment unit 2.

As can be seen from fig. 3, this air inlet device 24 is a single component capable of introducing air into the flue gas treatment unit 2. There is no other air inlet or other means for introducing air downstream of the flue gas treatment unit, where the air inlet means is positioned at the interface between the flue gas outlet 12 of the torrefaction device and the flue gas inlet 11 of the flue gas treatment unit.

This flue gas inlet 21 is shown in particular in fig. 4: on the upper upstream side of the flue gas treatment unit, a flue gas inlet 21 is formed by a pipe end. In the direction of the fume filtration subunit 22, the duct directs fume (dashed lines S1, S2) out of the outlet 11 of the torrefaction device.

According to the embodiment shown in fig. 4, in an enlarged view of the interface between the flue gas treatment unit and the torrefaction device, the air inlet arrangement 24 comprises a first wall 241 extending between and connecting the flue gas outlet 11 and the flue gas inlet 21. This first wall includes a number of holes 240 (four holes in this particular embodiment, but only two of the four holes are visible in the front view of fig. 4) to effect air introduction as indicated by the four arrows a.

Advantageously, these holes provide a loose connection of the flue gas outlet 11 with the flue gas treatment unit, while having the positive effect of limiting any pressure effects inside the baking chamber.

Along the circumference of the tube, these holes 240 encircle the flue gas inlet 21. Thus, these holes enable air intake as shown in the vertical upward direction as indicated by arrow a and similar to flue gas S1. The fact that the flue gas and air are introduced at the same point of the flue gas treatment unit provides an air flow and a flue gas flow in the same direction (here vertical and upward), which requires less suction force of the flue gas driver 23 and generates less noise. It can be seen that the flue gas treatment unit 2 does not comprise any other air inlet than the shown upstream inlet 24.

In alternative embodiments, the air inlet may have more or fewer holes 240, including only one hole.

Preferably, these holes 240 are protected by a fine grid or mesh to prevent any debris intrusion.

The size and shape of these holes 240 may vary. Fig. 5 schematically shows an air inlet device 24 with four very large holes 240, wherein the first wall 241 is limited to four bars connecting a part 248a connectable to the flue gas outlet of the baking apparatus to a part 248b connectable to the flue gas inlet of the flue gas treatment unit. The grid protects these macropores.

The design of the air inlet 24 (in particular its number and the area defined by the holes) is preferably defined as:

Limiting the pressure drop at the flue gas outlet 11 of the torrefaction device, as the pressure drop may affect the upstream processes of the torrefaction; this can be achieved by providing a sufficiently large integral air inlet. In particular, the design may be defined to provide a minimum ratio of air volume to flue gas volume to achieve a minimum speed of the flue gas driver components of the system.

And

preventing the flue gas S1 from flowing through these air inlets 24 into the ambient atmosphere, which may occur if these air inlets are too large. In the embodiment shown, the surrounding positions of the different inlets 24 ensure this effect.

Fig. 6 shows a specific embodiment of the air inlet device 24 comprising only three holes 240 in the front region 244 of the contour of the first wall 241. No holes are provided in other side and rear regions of the first wall 241.

If the system is used in a portion of a room that experiences turbulence in the air due to customer movement, door opening, etc., the use of such air heating devices in the system achieves orientation of the holes 240 in locations where the air is not or is not susceptible to turbulence.

Fig. 7A shows a specific embodiment of the air inlet device 24 comprising four holes 240 in a first wall 241 and an outer annular wall 242 surrounding the first wall 241. The two walls 241, 242 are separated by a gap 245. Within this gap, the air is not affected by external turbulence and can be drawn evenly through the holes 240 into the air inlet means and into the flue gas inlet of the flue gas treatment unit.

In addition, the outer annular wall 242 prevents the introduction of debris through the holes 240 and prevents the escape of smoke from these holes (due to air stabilization). This wall 242 also limits noise of air drawn through the air inlet device compared to embodiments without an outer annular wall.

Fig. 7B is an alternative embodiment of fig. 5A, wherein the outer wall includes two portions 242a, 242B, each of which surrounds a portion of the first wall that includes the aperture 240.

Fig. 8 shows a specific embodiment of the air inlet device 24 comprising an aperture 240 in the first wall 241 and a size adjustment member 246 for adjusting the size of said aperture 240. In this embodiment, the adjustment means consist of shutters which are orientable between a first position in which the aperture is fully open, to a second position in which the aperture is fully closed, and an intermediate position in which the aperture size is adjustable. In this embodiment, the adjustment member 246 may be controlled by a manual actuator 249, such as a screw.

Other types of size adjustment members may be used, such as covers that slide gradually by rotating or translating over the aperture. Fig. 10 shows an embodiment in which the size adjustment member is a cover 246 configured to partially or fully slide over the aperture 240 according to a rotational movement.

If several holes are provided, it is preferred that each of them has a corresponding size adjusting means. This provides the opportunity to close the aperture in one particular region 244, the effect of which is to protect the introduction of air, as described above.

The different adjustment members may be controlled by the same common actuator, but are preferably controlled by different actuators individually.

Fig. 9 shows an alternative form of the embodiment of fig. 6, in which the manual actuator is replaced by an automatic actuation means 247, such as a motor, which can be controlled by the control system of the system.

Since the temperature of the ambient air is typically at most 40 ℃, i.e. much lower than the temperature of the flue gas at the outlet of the baking device, the fact that air is introduced and mixed with the flue gas results in a reduced temperature of the flue gas S2 to be treated by the filtration subunit.

The air inlet means may be configured to effect the introduction of an air flow so as to cause the temperature of the mixture S2 to ensure an optimal treatment of the flue gases, for example in the case of a filtering subunit comprising an activated carbon filter 21 that works optimally at a temperature comprised between 50 ℃ and 65 ℃.

The ratio adjustments made by the flue gas driver power are managed to control the temperature in the flue gas treatment unit. In addition, other secondary conditions may be considered, such as:

At high flow rates, the contact time of the fumes with the filter is reduced. Since the high power of the flue gas driver means a high flow rate of flue gas through the flue gas treatment unit, this may lead to insufficient contact time in the different filters, especially in case of using an activated carbon filter 221, which has the effect of distributing contaminants to the atmosphere at the outlet 25 of the flue gas treatment unit.

The effect of such flue gas temperature control is in particular the efficient treatment of the flue gas by means of an activated carbon filter, thereby ensuring an efficient adsorption of VOCs and avoiding the emission of VOCs by the activated carbon filter itself at high temperatures, typically above 65 ℃.

When the air inlet means comprises actuating means 247 for adjusting the aperture size, the flow rate of air and the ratio of air to flue gas can be controlled by varying the aperture size instead of or in addition to the power adjustment of the flue gas driver.

The adjustment of the pore size may be done dynamically during the treatment of the flue gas generated by the baking device based on temperature measurements within the flue gas treatment unit: for example, the size may be reduced at the beginning of the baking operation, because the temperature of the flue gas is not high due to the heating inertia for heating the internal components of the flue gas treatment unit, and after a certain time the temperature increases, the pore size may be increased to introduce more fresh air within the flue gas.

With reference to fig. 3, 4, 12 and 9 or 10, the control system 3 will now be considered when the system comprises an actuation means 247 for the air inlet.

When the air inlet means 24 comprises automatic actuation means 247 for controlling the size adjustment member of the aperture 240, then alternatively or in addition to the control of the flue gas driver 23, the processing unit 30 is operable to:

receiving an input from a temperature sensor 26,

process the input according to a smoke treatment program code (or programmed logic) stored on the memory unit 31,

providing an output comprising control of the actuation means 247. As such, the process is more preferably performed by closed loop control using the input signal from the temperature sensor 26 as feedback.

If the temperature becomes too high, the size of the aperture 240 is increased to introduce a larger volume of ambient air A through the air inlet means 24 and mix more air with the flue gas S1, which has the effect of reducing the temperature of the flow of flue gas S2.

However, if the temperature becomes too low, the size of the aperture 240 is reduced to introduce a smaller volume of air environment A and mix less air with the flue gas S1, which has the effect of increasing the temperature of the flue gas S2. In this case, the processing unit is operable to prevent the size of the aperture 240 from being adjusted below a minimum value, thereby avoiding affecting the pressure within the baking apparatus, and still achieve the objective of limiting air intake by controlling the flue gas driver 23 and reducing the fan speed.

The advantage of controlling the temperature by adjusting the size of the holes 240 is that it has no or less effect on the noise generated by the flue gas driver than a solution that only controls the speed of the flue gas driver.

While the invention has been described with reference to the embodiments shown above, it should be understood that the invention as claimed is not in any way limited to these shown embodiments.

Various changes and modifications may be made without departing from the scope of the invention as defined in the following claims. Furthermore, if known equivalents exist for specific features, such equivalents should be incorporated as if explicitly set forth in this specification.

As used in this specification, the words "comprise", "comprising" and the like are not to be interpreted as having an exclusive or exhaustive meaning. In other words, these words are intended to mean "including, but not limited to".

List of references in the drawings：

Baking apparatus 1

Flue gas outlet 11

Roasting chamber 12

Top outlet 121

Flue gas treatment unit 2

Flue gas inlet 21

Hole 211

Flue gas filtration subunit 22

Activated carbon filter 221

PM filter 222, 223

Flue gas driver 23

Air inlet device 24

Hole 240

First wall 241

Outer walls 242, 242a, 242b

Mesh 243

Region 244

Gap 245

Size adjusting member 246

Actuating device 247

Interfaces 248a, 248b

Manual actuator 249

Outlet 25

Temperature sensor 26

Guide duct 27

Control system 3

Processing unit 30

Memory cell 31

User interface 32

Power source 33

System 100

Claims

1. A system (100) for roasting coffee beans, the system comprising:

-a baking apparatus (1) generating flue gas, and

a fume treatment unit (2) configured to collect and treat fumes generated by said baking apparatus,

wherein:

-the baking apparatus comprises a flue gas outlet (11), and

-the flue gas treatment unit comprises:

a flue gas inlet (21) configured to collect flue gas,

a smoke filtering subunit (22),

a flue gas driver (23) configured to circulate flue gas from the flue gas collection device to an outlet (25) of the flue gas treatment unit through the flue gas treatment unit,

wherein the system comprises an air inlet device (24) configured to mix the flue gas generated by the torrefaction arrangement (1) with ambient air in order to control the temperature of the flue gas within the flue gas filtration subunit (22),

wherein the air inlet means (24) is positioned at a location upstream of the smoke filtering subunit (22).

2. The system according to claim 1, wherein the flue gas filtration subunit (22) comprises at least an activated carbon filter (221).

3. The system according to claim 2, wherein the flue gas filtration subunit (22) comprises at least one additional filter (222, 223) that works without heating.

4. A system according to claim 3, wherein the fume filtration subunit (22) comprises, in order: a HEPA filter (222), an electrostatic precipitator (223) and an activated carbon filter (221).

5. The system according to any of claims 1-4, wherein the air inlet device (24) is positioned and designed to introduce both air and flue gas at the same point within the flue gas treatment unit (2).

6. The system according to any one of claims 1-4, wherein the flue gas treatment unit (2) comprises at least one temperature sensor (26) configured for monitoring the temperature within the unit.

7. The system according to any one of claims 1-4, wherein the air inlet device (24) comprises:

-a first wall (241) extending between the flue gas outlet (11) of the baking device and the flue gas inlet (21) of the flue gas treatment unit, and

-at least one hole (240) through the first wall.

8. The system of claim 7, wherein:

-the first wall (241) of the air inlet device (24) comprises: at least two bars connecting the flue gas outlet (11) of the baking device to the flue gas inlet (211) of the flue gas treatment unit, and

-the space extending between two adjacent bars defines an aperture (240).

9. The system of claim 7, wherein only one region (244) of the contour of the first wall of the air inlet device includes the at least one aperture (240).

10. The system of claim 7, wherein the air inlet device (24) includes an outer wall (242) surrounding at least a portion of the first wall (241) including the at least one aperture (240), and the first wall and the outer wall are separated by a gap (245).

11. The system of claim 7, wherein the air inlet device (24) includes at least one size adjustment member (246) to adjust a size of the at least one aperture (240) included in the first wall (241).

12. The system of claim 11, wherein the system comprises at least one actuation device (247) to control the size adjustment component (246), and the system comprises a control system (3) operable to control the actuation device (247).

13. The system according to claim 12, wherein the flue gas treatment unit (2) comprises at least one temperature sensor (26) configured for monitoring a temperature within the unit, and wherein the control system (3) is arranged to control the at least one actuation device (247) of the at least one size adjustment component based at least on the monitored temperature within the flue gas treatment unit.

14. The system according to claim 13, wherein the control system is arranged to control the actuation means (247) and the flue gas driver (23) of the flue gas treatment unit based at least on the monitored temperature within the flue gas treatment unit.

15. The system according to claim 14, wherein the control system is arranged to control the flue gas driver (23) of the flue gas treatment unit based at least on the size of the at least one aperture (240).

16. The system according to claim 12, wherein the size of the at least one hole is fixed, and wherein the flue gas treatment unit (2) comprises at least one temperature sensor (26) configured for monitoring the temperature within the unit, and wherein the control system (3) is arranged to control the flue gas driver (23) of the flue gas treatment unit based on temperature measurements provided by the temperature sensor.

17. The system according to any of claims 1-4, wherein the air inlet device (24) is part of the torrefaction apparatus (1) or part of the flue gas treatment unit (2) or is a separate device connectable to the torrefaction apparatus and the flue gas treatment unit.

18. The system of claim 10, wherein the outer wall completely surrounds the first wall.

19. A fume treatment unit (2) configured to collect and treat fumes generated by a baking apparatus, the fume treatment unit comprising:

a flue gas inlet (21) configured to collect flue gas, and

a smoke filtering subunit (22), and

wherein the flue gas treatment unit comprises an air inlet device (24) configured to mix the flue gas with ambient air before circulating the flue gas through the flue gas filtration subunit (22).

20. A flue gas treatment unit (2) according to claim 19, wherein the air inlet means (24) is connected to the flue gas inlet (211) and the means (24) comprise:

-a first wall (241) extending and protruding from the flue gas inlet (21), and

-at least one hole (240) through the first wall.

21. Method for roasting coffee beans and filtering flue gas generated during roasting of the beans with a system according to any one of claims 1 to 18, wherein the flue gas driver (23) of the flue gas treatment unit is controlled to adjust the amount of ambient air within the flue gas treatment unit in order to control the temperature of the flue gas within the flue gas filtering subunit (22).

22. A method according to claim 21, wherein the flue gas treatment unit comprises an activated carbon filter (221) and the flue gas driver (23) of the flue gas treatment unit is controlled to introduce an amount of ambient air in the flue gas in order to obtain a temperature of the flue gas of at most 65 ℃ at the activated carbon filter (221).

23. The method of claim 22, wherein the temperature of the flue gas obtained at the activated carbon filter (221) is at least 50 ℃.

24. Method for roasting coffee beans with a system according to any one of claims 11 to 16 and filtering flue gas generated during roasting of the beans, the method comprising the step of adjusting the size of the at least one aperture (240) comprised in the first wall of the air inlet device in order to control the temperature within the flue gas filtering subunit (22).

25. The method of claim 24, wherein the size of the at least one aperture (240) is increased in order to decrease the temperature, or the size of the at least one aperture (240) is increased in order to increase the temperature.